Re: MODULEand USE versus Argument Passing

John Harper wrote: 
In article <d9us2s$ncr$1@xxxxxxxxxxxxxxxxxx>,
E. Robert Tisdale <E.Robert.Tisdale@xxxxxxxxxxxx> wrote:


Global variables are *always* a bad idea.
Never pass function arguments through modules or common storage.

Really? Suppose I am using one of the NAG routines, e.g. d01akf, to calculate integral from a to b of f(x,y) dx for various values of y. The NAG specification says (irrelevant detail omitted; and REAL should be replaced by REAL(kind(1.0d0)) with many compilers) 

(snip)

and f must be declared as EXTERNAL in the (sub)program from which d01akf is called, and it must be declared as a REAL(DP) function of one REAL(DP) variable, not two.

I had thought the way to get y into f was by COMMON before f90, and by using a module nowadays. What would Robert have me do? 

Not to agree with Robert (I don't) but I don't believe this is the
best solution.  It is the Fortran solution since Fortran I, though.
Note, though, that it isn't reentrant.

(Much of the standard C library isn't reentrant either, but I don't
think I will have much say in changing it.)

In C I would add an additional parameter which is a void pointer
such that one could pass a structure pointer through to the called routine. That allows for a reentrant solution, pointers to different structures being passed as needed.

I don't know that there is a Fortran solution similar, though.

-- glen

.

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